Low- and high-z highly accreting quasars in the 4D Eigenvector 1 context

TL;DR

This paper explores the properties of highly accreting quasars across different redshifts using the 4D Eigenvector 1 framework, highlighting their potential as cosmological probes due to their unique physical characteristics.

Contribution

It extends the 4D Eigenvector 1 approach to identify highly accreting quasars beyond low redshift Narrow Line Seyfert 1s, suggesting they have a specific physical structure and cosmological relevance.

Findings

Highly accreting quasars have distinctive properties in 4D Eigenvector 1 space.

Selection criteria can identify sources with a thick, optically thick accretion disk.

Their Eddington ratio saturates near unity, useful for cosmology.

Abstract

Highly accreting quasars are characterized by distinguishing properties in the 4D eigenvector 1 parameter space that make them easily recognizable over a broad range range of redshift and luminosity. The 4D eigenvector 1 approach allows us to define selection criteria that go beyond the restriction to Narrow Line Seyfert 1s identified at low redshift. These criteria are probably able to isolate sources with a defined physical structure i.e., a geometrically thick, optically thick advection-dominated accretion disk (a "slim" disk). We stress that the importance of highly accreting quasars goes beyond the understanding of the details of their physics: their Eddington ratio is expected to saturate toward values of order unity, making them possible cosmological probes.